Radio frequency data communications device with adjustable receiver sensitivity and method

ABSTRACT

A device has a monolithic semiconductor integrated circuit with integrated circuitry, interrogation receiving circuitry provided on the monolithic integrated circuit forming at least part of the integrated circuitry and configured to receive an interrogation signal from the interrogator unit, an antenna electrically coupled to the interrogation receiving circuitry and configured to communicate with the remote interrogator unit, a power source electrically coupled to the integrated circuitry and configured to generate operating power for the communications device, and at least one of the antenna and the interrogation receiving circuitry having reconfigurable electrical characteristics, the electrical characteristics being reconfigurable to selectively tune the at least one of the antenna and the interrogation receiving circuitry within a range of tuned and detuned states to realize a desired receiver sensitivity of the communications device. Additionally, a method for tuning receiver sensitivity and/or transmitter sensitivity according to construction of the above device is disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. patent application Ser. No. 10/315,427,filed Dec. 9, 2002, by Mark E. Tuttle and John R. Tuttle, entitled“Radio Frequency Data Communications Device with Adjustable ReceiverSensitivity and Method”, now U.S. Pat. No. 6,781,508, which in turn is acontinuation of U.S. patent application Ser. No. 09/961,204, filed Sep.21, 2001, now U.S. Pat. No. 6,509,837, which is a continuation of U.S.patent application Ser. No. 08/708,164, filed Aug. 29, 1996, now U.S.Pat. No. 6,466,131, granted Oct. 15, 2002, which in turn claims priorityfrom U.S. Provisional Application Ser. No. 60/023,321, filed Jul. 30,1996, titled “A Radio Frequency Data Communications Device withAdjustable Receiver Sensitivity and Method” and naming Mark E. Tuttleand John R. Tuttle as inventors.

TECHNICAL FIELD

This invention relates to radio frequency communication devices, andmore particularly to an adjustable radio frequency interrogator tag andmethod of adjusting transponder sensitivity.

BACKGROUND OF THE INVENTION

As large numbers of objects are moved in inventory, productmanufacturing, and merchandising operations, there is a continuouschallenge to accurately monitor the location and flow of objects.Additionally, there is a continuing goal to interrogate the location ofobjects in an inexpensive and streamlined manner. Furthermore, there isa need for tag devices suitably configured to mount to a variety ofobjects including goods, items, persons, or animals, as well as anymoving or stationary and animate or inanimate object. One way oftracking objects is with an electronic identification system.

One presently available electronic identification system utilizes amagnetic field modulation system to monitor tag devices. A controller orinterrogator unit creates a magnetic field that becomes detuned when thetag device is passed through the magnetic field. In some cases, the tagdevice may be alternatively tuned and detuned in a sequence unique tothe tag device in order to distinguish between a number of differenttags, each having a distinct identify sequence. Typically, the tagdevices are entirely passive, eliminating the need for a portable powersupply which results in a small and portable package. However, thisidentification system is only capable of distinguishing a limited numberof tag devices, over a relatively short range, limited by the size ofthe resulting magnetic field. Detuning is the means of encoding theidentification number of the tag device or its data.

Another electronic identification system utilizes an RF transponderdevice affixed to an object to be monitored, in which a controller orinterrogator unit transmits an interrogation signal to the device. Thedevice receives the signal, then generates and transmits a responsivesignal. The interrogation signal and the responsive signal are typicallyradio-frequency (RF) signals produced by an RF transmitter circuit.Since RF signals can be transmitted over greater distances than magneticfields, RF-based transponder devices tend to be more suitable forapplications requiring tracking of a tagged device that may not be inclose proximity to an interrogator unit. However, when a large number ofdevices are utilized, the interrogator unit triggers frequent wake-up ofeach device. As a result, responsive signals are frequently generated.For the case of a battery powered device, the life of the battery isseverely diminished due to frequent unintentional wake-ups of thedevice. Therefore, there is a need to produce tags having differentreceiver sensitivities, and to produce tags having either factory oruser adjustable sensitivity. Such constructions are the subject of thisinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

FIG. 1 is a front view of an employee badge providing the device of thisinvention.

FIG. 2 is a front view of a radio frequency identification tag of thisinvention.

FIG. 3 is a block diagram of an electronic identification systemillustrating communication between an interrogator unit and the tag ofFIG. 2.

FIG. 4 is a plan view of a monolithic semiconductor integrated circuitutilized in the device of FIG. 2 illustrating an integrated circuitrylayout configured for use with a hybrid antenna.

FIG. 5 is an alternative construction of a monolithic semiconductorintegrated circuit from that depicted in FIG. 4, wherein the antenna isformed directly on the integrated circuit.

FIG. 6 is an enlarged partial view taken generally from encircled region6 of FIG. 4 depicting a discretely slit portion.

FIG. 7 is an enlarged partial view taken generally from encircled region7 of FIG. 4 depicting a stepwise removed portion.

FIG. 8 is a diagrammatic side sectional view illustrating mounting of anintegrated circuit, battery and antenna to the tag device of FIG. 2.

FIG. 9 is a diagrammatic side sectional view illustrating an alternativewire bonding technique for mounting the integrated circuit, battery andantenna to the tag device of FIG. 2.

FIG. 10 is a diagrammatic side sectional view illustrating anotheralternative mounting technique using tape automated bonding (TAB) ofleads to electrically bond the integrated circuit, battery and antennatogether on the tag device of FIG. 2.

FIG. 11 is a flowchart illustrating how receiver sensitivity can bechanged in accordance with some aspects of the invention.

FIG. 12 is a flowchart illustrating how transmitter sensitivity can bechanged in accordance with some aspects of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This disclosure of the invention is submitted in furtherance of theconstitutional purposes of the U.S. Patent Laws “to promote the progressof science and useful arts” (Article 1, Section 8).

According to an aspect of this invention, an adjustable radio frequencydata communications device comprises a monolithic semiconductorintegrated circuit having integrated circuitry; interrogation receivingcircuitry provided on the monolithic integrated circuit forming at leastpart of the integrated circuitry and configured to receive aninterrogation signal from the interrogator unit; an antenna electricallycoupled to the interrogation receiving circuitry and configured tocommunicate with the remote interrogator unit; a power sourceelectrically coupled to the integrated circuitry and configured togenerate operating power for the communications device; and at least oneof the antenna and the interrogation receiving circuitry havingreconfigurable electrical characteristics, the electricalcharacteristics being reconfigurable to selectively tune the at leastone of the antenna and the interrogation receiving circuitry within arange of tuned and detuned states to realize a desired receiversensitivity of the communications device.

According to another aspect of this invention, an adjustable radiofrequency data communications device comprises a monolithicsemiconductor integrated circuit having integrated circuitry;transmitter circuitry provided on the monolithic integrated circuit andforming at least part of the integrated circuitry; an antennaelectrically coupled to the transmitter circuitry and configured tocommunicate with the remote interrogator unit; a power sourceelectrically coupled to the integrated circuitry and configured togenerate operating power for the communications device; and at least oneof the antenna and the transmitter circuitry having reconfigurableelectrical characteristics, the electrical characteristics beingreconfigurable to selectively tune the at least one of the antenna andthe transmitter circuitry within a range of tuned and detuned states torealize a desired transmitter sensitivity of the communications device.

According to a third aspect of this invention, an adjustable radiofrequency data communications device comprises: a printed circuit boardhaving printed circuitry; interrogation receiving circuitry provided onthe circuit board electrically coupled to the integrated circuitry andconfigured to receive an interrogation signal from the interrogatorunit; an antenna electrically coupled to the interrogation receivingcircuitry, the antenna configured to receive the interrogation signalfrom the interrogator unit and deliver the interrogation signal to theinterrogation receiving circuitry; a power source electrically coupledto the printed circuitry and configured to generate operating power forthe communications device; and at least one of the antenna and theinterrogation receiving circuitry having reconfigurable electricalcharacteristics, the electrical characteristics being reconfigurable toselectively tune at least one of the antenna and the interrogationreceiving circuitry within a range of tuned and detuned states torealize a desired detuned receiver sensitivity of the communicationsdevice.

According to a fourth aspect of this invention, a method of adapting aradio frequency data communications device for use with a remoteinterrogator unit comprises the steps of: providing transpondercircuitry; providing an antenna electrically coupled to the transpondercircuitry for communicating with a remote interrogator unit; andselectively tuning at least one of the antenna and the transpondercircuitry within a range of tuned and detuned states to realize adesired receiver sensitivity responsive to an interrogation signaltransmitted by the interrogator unit.

Referring more particularly to the drawings, FIG. 1 illustrates anemployee identification badge 10 embodying this invention. The badge ofthis invention in one embodiment has a radio-frequency datacommunication device 12 laminated to a back face of a plastic card 11,wherein the card forms the visible portion of the badge. Preferably, thecommunication device 12 is bonded to the back face of the card byembedding it within a thin bond line of epoxy-based material.Alternatively, the communication device 12 is embedded into the plasticcard 11. The communication device 12 has an antenna 14 that iselectrically connected with a transponder silicon-chip integratedcircuit 16 to form a transmitting and receiving device. Additionally,the device has a battery 18 that is electrically connected to theintegrated circuit in order to power the device when it is transmittingand receiving radio-frequency (RF) signals between itself and anotherdevice. Preferably, the front face of the badge also has visualidentification features including an employee photograph as well asidentifying text.

Preferably, the antenna 14 is constructed and arranged to form a foldeddipole antenna, consisting of a continuous conductive path, or loop ofmicrostrip. The terminal ends of the loop each form a conductive leadsimilar to leads 37 in FIG. 4 that electrically interconnects with atransponder circuit 30 on the integrated circuit 16, as depicted in usein an alternative embodiment in FIG. 4 and discussed in greater detailbelow. Alternatively, the antenna can be constructed as a continuousloop antenna 22, as depicted in FIGS. 2-3 and discussed in greaterdetail below.

Preferably, the battery 18 is a thin profile button-type battery forminga small, thin energy cell more commonly utilized in watches and smallelectronic devices requiring a thin profile. A conventional button-typebattery has a pair of electrodes, an anode formed by one face and acathode formed by an opposite face. Exemplary button-type batteries aredisclosed in several pending U.S. patent applications including U.S.patent application Ser. No. 08/205,957, titled “Button-Type BatteryHaving Bendable Construction and Angled Button-Type Battery”, listingMark E. Tuttle and Peter M. Blonsky as inventors (now U.S. Pat. No.5,432,027); and U.S. patent application Ser. No. 08/321,251, titled“Button-Type Batteries and Method of Forming Button-Type Batteries”,listing Mark E. Tuttle as inventor (now U.S. Pat. No. 5,494,495). Thesepatent applications and resulting patents are hereby incorporated byreference as if fully included herein.

FIG. 2 depicts an alternative construction for a radio-frequency datacommunications device 12′ constructed as an identification postage stamp20. Device 12′ has a semiconductor-based transponder integrated circuit16, a battery 18, and an antenna 22. Preferably, the antenna isconstructed from a continuous piece of conductive microstrip configuredin the shape of a square to form a loop antenna. Preferably, the postagestamp is formed from a thin sheet, or card 21 of plastic material havinga thickness of about 0.005 inches, and a final width and height of about1.25 inches. As was the case for the badge 10 of FIG. 1, preferably, thedevice 12′ is bonded to a back face of the plastic card by embedding itin a thin layer of non-conductive epoxy material. The final thickness isabout 0.030 inches. Further details of the construction will bediscussed below with reference to FIG. 8.

Preferably, the integrated circuit 16, antenna 22, and battery 18 form atransponder device capable of transmitting and receiving RF signals witha radio-frequency interrogator unit 26, shown in FIG. 3 asradio-frequency communication system 24. Preferably, the interrogatorunit includes an antenna 28, as well as dedicated transmitting andreceiving circuitry, similar to that implemented on integrated circuit16. One example of an interrogator unit implemented in combination witha transponder unit is disclosed in U.S. Pat. No. 4,857,893, herebyincorporated by reference. Generally, the interrogator unit transmits aninterrogation signal 27 via antenna 28. The transponder device 12′, inthis case stamp 20, receives the incoming interrogation signal withantenna 22. Upon receiving signal 27, device 12′ preferably responds bygenerating and transmitting a responsive signal 29. Preferably, theresponsive signal 29 is encoded with unique information that uniquelyidentifies, or labels the stamp 20, as well as any object on which thestamp is affixed.

With the above described interrogator/transponder communication system24, a big benefit is provided over prior art devices that utilizedmagnetic field effect systems because a large number of uniquelyidentifiable tags can be constructed. With the old magnetic field effectsystems, a passive element tag modified a magnetic field when moved inproximity to an interrogator unit, thereby allowing electronicidentification and detection of the tag. However, in order to identifyparticular tags, each tag was alternately tuned and detuned in a certainsequence in order to distinguish it from other tags. It is easy to seethat such a system has at best a very limited ability to discriminatebetween tags. In contrast, a large amount of information can be carriedon the responsive signal 29, allowing for detailed description of thedevice 12′.

As a result, such a system 24 can be used, for example, to monitor largewarehouse inventories having many unique products needing individualdiscrimination to determine the presence of particular items within alarge lot of products. However, a significant problem is posed by suchimplementations where a battery is used to supply power to the devicessince each time an interrogation signal 27 is received, each devicewithin receiving range of the signal will “wake up”, thereby consumingvaluable power and reducing the life of the battery. Typically, the lifeof the device is also reduced commensurately since the battery ispreferably permanently sealed inside either a badge 10, a stamp 20, orsome other similar tag.

One reason for sealing the battery within the tag is to simplify thedesign and construction, as well as to reduce the cost of producing thetag. Another is to seal the battery within the tag, thereby protectingit from moisture and contaminants. A third reason is to enhance thecosmetic appeal of the tag by eliminating the need for an access port ordoor otherwise necessary to insert and remove the battery. When thebattery is discharged, the entire badge or stamp is then discarded.Hence, it is desirable to maximize the life of the battery by minimizingpower consumption.

Preferably, the transponder device 12′ is electrically powered by abattery 18. In order to conserve the power supplied from battery 18,preferably, device 12′ goes into a sleep, or battery conserving stand-bymode of operation during long time periods where no interrogation signal27 is received by the device. Preferably, a low current circuitperiodically wakes up the device every sixteen milliseconds in order tocheck if any RF signals are being detected by the device. Upon detectionof such signals, the device fully wakes up, returning it to a full poweroperating mode. In order to further extend the life of battery 18, thereceiver sensitivity of the transponder device 12′ is preferably tunedover a range of tuned and detuned states in order to modify the abilityof the device to detect signal 27, and therefore adjust the tendency forthe device to wake up.

Preferably, the receiver sensitivity of the device is adjusted byreconfiguring the electrical characteristics (circuitry) of the circuitforming the transponder device. One way to adjust the receiversensitivity is to adjust the sensitivity, or impedance of the antenna.Another way is to adjust or switch in different circuit elements in thetransponder device, thereby realizing different circuit configurations,as shown in FIG. 11. Additionally, the transmitting sensitivity for thetransponder device can be adjusted in essentially the same manner, asshown in FIG. 12. Techniques of this invention for adjusting thetransmitting and receiving sensitivities for an antenna will bediscussed below with reference to implementations depicted generally inFIGS. 4-7. Techniques of this invention for adjusting the transmittingand receiving sensitivities for circuit elements of the transponderdevice will also be discussed below with reference to implementationsdepicted generally in FIGS. 4 and 5.

FIG. 4 depicts the particular construction of integrated circuit 16 asimplemented on the devices 10 and 20 of FIGS. 1 and 2, respectively. Asshown in FIG. 4, the integrated circuit is formed from a singlemonolithic silicon chip construction wherein the integrated circuit, orwafer receives an array of transponder circuits 30, logic circuits 32,memory control logic circuits 34, and a programmable memory array 36according to standard semiconductor wafer processing steps.Additionally, pairs of conductive die pads 38 and 40 are formed on theintegrated circuit in order to facilitate electrical connection with theantenna 22 and battery 18, respectively. Preferably, circuits 30 areelectrically coupled with the conductive die pads 38 and 40 by way ofsections of conductive microstrip 39 and 41, respectively.

For illustrative purposes, antenna 22 is depicted in electricallyconductive and bonded relationship with pads 38 via legs 37, althoughthe preferred assembly technique, illustrated in FIG. 8 and discussedbelow, involves a flip-chip epoxy bonding technique wherein the antenna22 is actually printed onto the back face of the plastic card 21 formingthe postage stamp 20, after which the integrated circuit is bonded tothe antenna, as well as to the battery, using a conductive epoxy.

FIG. 4 depicts the relationship of the transponder circuits 30 relativeto antenna 22 which electrically connects directly to the transpondercircuits, and the battery (not illustrated in this Figure), and whichalso electrically connects directly to the transponder circuits.Preferably, the logic circuits 32, the memory control logic 34, and theprogrammable memory array 36 electrically connect with the transpondercircuits 30. In this manner, battery 18, once electrically connected topads 40, powers all of the circuits 30-36.

According to one technique for tuning the transceiving sensitivity of adevice 12′ carried by a tag, for example stamp 20, the antenna is lasertrimmed after it is formed in order to reconfigure a conductive portionof the integrated circuit, thereby modifying the transceivingsensitivity of the device 12′ by changing its impedance. For purposes ofthis disclosure, transceiving sensitivity includes transmitter andreceiver sensitivity. Alternatively, just the transmitting sensitivityor the receiving sensitivity can be tuned. Further alternatively,separate transmitting and receiving antennas can be independently tuned.For example, a receive antenna and a separate backscatter transmitantenna can be used, and for one case, just the receive antenna istrimmed in order to tune it. Furthermore, for purposes of thisdisclosure, tuning refers to either tuning or detuning a radio-frequencytransponder device. Finally, adjustment of the antenna impedancerelative to the impedance of the transponder circuits imparts a tuningto the combined electrical circuit. For example, when the antennaimpedance matches the transponder circuit impedance and the two areconnected in series, the circuit is optimally tuned. Similarly, variousdegrees of impedance mis-matching produce corresponding levels ofdetuning.

Preferably, transponder circuit 30, logic circuits 32 and memory controllogic 34 are implemented as a combination of hardware circuit elementsand software. With respect to the software components, preferably, thesoftware is implemented in the programmable memory array 36.

FIG. 6 depicts one method for tuning the antenna 22 of FIG. 4, wherein aportion of conductive microstrip forming the antenna is selectivelyremoved along each edge with a laser, forming a transverse slit 52. Theresulting step-width change in the microstrip antenna causes a change inimpedance, thereby changing the tuned state of the antenna from theoriginally produced state. In this manner, a large lot of identicalantennas can be mass produced at the factory, after which the antennascan be laser trimmed to create batches of antennas having tailored tunedcharacteristics, e.g. specific receiving sensitivities.

Preferably, the antenna 22 of FIGS. 4 and 6-7 is printed onto the backside of card 21, forming the microstrip loop antenna. For example, theantenna can be silk screened onto the card with a conductive polymerthick film. Alternatively, a conductive silver filled epoxy can be used.Further details of this construction will be provided below whendescribing FIG. 8. Alternatively, the antenna can be formed from aseparate piece of conductive material, for example, from a piece of wireor conductive ribbon that is glued to the back of the card.

FIG. 7 illustrates another method for tuning the antenna of FIG. 4,wherein the microstrip antenna is produced with widened regions, forminglaterally extending pairs of stubs 54. The pairs of stubs impart changesin the impedance of the resulting antenna 22. Additionally, the stubsfacilitate laser removal of portions 56, leaving enshortened stubs 58.As a result, the impedance of the antenna 22 can be changed, therebytuning the antenna based on the amount of conductive material removedfrom portions 56, as well as from the number of portions 56 removed froman array along the microstrip.

FIG. 5 illustrates a third method for tuning an antenna on asemiconductor transponder integrated circuit 46 having a coil-shapedantenna 48 formed directly on the integrated circuit in the form ofmicrostrip with one of several presently known standard semiconductordeposition techniques. Antenna 48 is preferably formed with a conductivebridge line 50 similar to conductive microstrip lines 39 and 41 thatshunts conduction between adjacent coils of the antenna. After theantenna is produced, at least part of the conductive bridge line 50 canbe removed, either mechanically or by laser trimming in order to tunethe antenna to a desired state. By selectively cutting the bridge line50, the effective conducting length of the antenna is modified,realizing one or several possible length antennas defined by the numberand size of each coil, and any remaining portion of the bridge.Preferably, an insulating layer of material is deposited on top ofconductive leads 41 during manufacture in order to insulate the leadsfrom shorting out coils on the antenna 48. Alternatively, numeral 46 ofFIG. 5 can represent a printed circuit board having integrated circuitryand hybrid circuit elements attached to the circuitry, forming thecircuits 30-36 and antenna 48. For a device of this inventionimplemented on a printed circuit board, the inventive contributionconsists of intentionally detuning the transponder sensitivity of thetag device.

For the case where the receiver sensitivity of the device is adjusted byreconfiguring the transponder circuits, the receiver sensitivity can bemodified by electrically modifying the receiver circuit on theintegrated circuit itself. For example, a plurality of parallelcircuits, each having a different impedance or amplification factor arealternately switched into an electrically conductive configurationwithin the transponder circuit. Different fixed matching networks 84,86, 88, 90 (see FIG. 5) can be alternately switched into connectionwithin the circuit, as shown in FIG. 11.

One way to achieve the switching is to provide temporary contactconnections on the integrated circuit (not shown) for forming atemporary electrical connection at the factory, allowing for factorysetup of one of the matching networks within circuits 30 to realize aspecific tuned condition for a transponder device 12. For example, anarray of resistive and/or capacitive elements can be provided onparallel circuit legs, each configured with a physical switch forconnecting and disconnecting the leg from the transponder circuit, suchthat each leg imparts a different circuit impedance, and hence, adifferent tuning. Another way is to implement a software switchingroutine that allows either factory or user switching of differentcircuit implementations within the transponder circuits 30, with actualcircuit elements or with a software routine implemented in memory 36 andtriggered by interrogation signals 27 received from the interrogatorunit 26 depicted in FIG. 3 to realize a software-based circuitimplementation. Additionally, each circuit leg can have an amplifierconfigured to impart a distinct tuning level to the circuit whenswitched into connection with the circuit. Hence, the transpondercircuit realized on the integrated circuit is modified to change thecircuit impedance, thereby realizing a different receiving sensitivityfor the device. The same technique can be used to tune the transmittingsensitivity. Additionally, a hybrid element such as a trim pot can beconnected to the circuits 30 of the integrated circuit to allowadjustment, or tuning of the circuits by either a manufacturer or auser.

Another reason for providing a tuning feature on RF data communicationdevices such as tags 10 and 20 is to allow a manufacturer to producelarge lots of identical integrated circuits and antennas, therebyenabling a cost savings resulting from large scales of production.Furthermore, by producing runs of identical devices, variables can bebetter controlled, enabling production of more uniform product whichincreases the amount of acceptable yield. After manufacture, theintegrated circuits and/or antennas can be tuned by one of thetechniques of this invention in order to create tuned tag devices havingparticular receiving and/or transmitting sensitivities.

For example, stamps 20 can be mass produced, then the antenna 22 can betuned to impart one of three receiver sensitivities of 5 feet, 20 feetor 100 feet. One customer may need tags having only one of the aboveoperating ranges. Another customer may need all three, placing the leastsensitive tags on objects where frequent inadvertent wake up calls froman interrogator are undesirable. When it is necessary to wake up thedevice, the interrogator is positioned within the five foot range inorder to activate the device, resulting in a responsive signal 29.Additional applications requiring employee badges 10 having varyingdegrees of receiver sensitivity can easily be envisioned.

FIG. 8 shows an exemplary technique for assembling the postage stamp 20.The same technique can be used to assemble the badge 10 or any othersimilarly constructed tag having a rigid support or substrate similar toplastic cards 11 and 21. First, antenna 22, conductive pads 66-68 andconductive microstrip leads 69 are printed onto a back face of the sheetof material. Preferably, the above elements, or conductors aresimultaneously printed onto the back of a large sheet of plasticmaterial with a conductive silver printed thick film. Later, the cardsare individually separated (after complete assembly), or cut from thesheet. Pads 66 form enlarged connection points for the antenna 22, incontrast to the pads 37 formed directly from the end portions of theantenna 22 in FIG. 4. Next, the sheet is positioned front face down ontoa rigid support plate 62. Then integrated circuit, or chip 16 is mountedto pads 66 and 67 with conductive beads of epoxy 70. Finally, thebattery 18 is bonded along its bottom face with a bead of conductiveepoxy 70 to the sheet, on each card, after which conductive epoxy 70 isused to electrically connect the opposite terminal or top of the batterywith a corresponding conductive die pad 68. The antennas and electricalcomponents are then electrically tested and/or trimmed, if necessary,prior to being encapsulated.

Subsequently, a bead of hot melt glue forming a dam 64 sized to conformgenerally to the outer peripheral shape of the sheet 21 is placed overthe back of the card. The dam functions as an outer template while athin layer of non-conductive epoxy (not shown) is applied to the back ofthe sheet 21, preferably hermetically sealing in (or encapsulating) theintegrated circuit, antenna and battery. Subsequently, the sheet isseparated, or singulated to form separate cards. In this manner, a largenumber of devices are assembled onto a single sheet, after which theyare separated. Preferably, the thin coat of epoxy consists of a coating,barely thick enough to cover over the components forming the device 12′.One benefit provided by this construction technique is the eliminationof any visible bumps in the tag which can result when constructing thetag by heat sealing two or more pieces of plastic card together to trapthe device 12′ therein. However, a lesser preferred construction of thisinvention envisions forming the tag, e.g. badge 10, stamp 20, or someother tag, with such a heat sealed sandwich of plastic cards.Furthermore, for constructions using a printed circuit board, the tagcan be formed from a case inside of which the board is mounted.

Preferably, the above technique for mounting integrated circuit 16 tocard 21 consists of a flip-chip mounting technique. One example of aflip-chip mounting technique is disclosed in U.S. patent applicationSer. No. 08/166,747, titled “Process of Manufacturing an ElectricalBonding Interconnect Having a Metal Bond Pad Portion and Having aConductive Epoxy Portion Comprising an Oxide Reducing Agent”, listingRickie C. Lake and Mark E. Tuttle as inventors (now U.S. Pat. No.5,480,834), and herein incorporated by reference.

FIG. 9 depicts an alternative method for electrically connecting theintegrated circuit 16 to the antenna 22 and battery 18 with conductivewires. In this construction, the integrated circuit 16 is adhesivelybonded to the back face of card 21, between the bonding pads 37 of theantenna 22 and the battery 18. Similarly, the battery 18 is bonded alonga bottom face to pad 68. Subsequently, a wire 76 and 78 is used toconnect each of the integrated circuit pads 38 and 40, respectively, toantenna bonding pads 37 and the top and bottom of battery 18,respectively. Preferably, each wire is soldered to the associated padsand battery. Alternatively, the wires can be electrically mounted usingconductive epoxy.

FIG. 10 depicts another alternative method for electrically connectingthe integrated circuit 16 to the antenna 22 and battery 18 withconductive leads 80 and 82, respectively. Preferably, one end of eachlead 80 and 82 is bonded to a pad 38 and 40 on the integrated circuit,respectively, and the other end is bonded to pad 37, and pad 67 and thetop of battery 18, respectively, using conductive epoxy. Alternatively,the leads can be soldered at each end to the respective components.Preferably, the battery is bonded to the back face of card 21 byapplying conductive adhesive between the battery and pad 68. Preferably,the integrated circuit is bonded along a bottom face to the back side ofcard 21.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

1. An adjustable radio frequency identification device for use with aremote interrogator unit, the device comprising: a monolithicsemiconductor integrated circuit having integrated circuitry;transmitter circuitry provided on the monolithic integrated circuit andforming at least part of the integrated circuitry; an antennaelectrically coupled to the transmitter circuitry and configured tocommunicate with the remote interrogator unit; and at least one of theantenna and the transmitter circuitry having reconfigurable electricalcharacteristics, the electrical characteristics being reconfigurable toselectively tune the at least one of the antenna and the transmittercircuitry for sensitivity within a range of tuned and detuned states topurposely reduce transmitter range of the device in response to acommand from the remote interrogator unit.
 2. An adjustable radiofrequency identification device in accordance with claim 1 wherein thetransmitter circuitry has at least one circuit with at least oneselectively tunable circuit element electrically reconfigurable tomodify the transmission range of the transmitter circuitry.
 3. Anadjustable radio frequency identification device in accordance withclaim 2 wherein the at least one circuit comprises a plurality of fixedmatching networks and circuitry configured to selectively switch one ofthe fixed matching networks into electrical connection with thetransmitter circuitry in order to adjust tuning of the transmittercircuitry and the antenna.
 4. An adjustable radio frequencyidentification device in accordance with claim 2 wherein the at leastone circuit comprises an adjustable circuit element which selectivelycauses the transmitter circuitry and the antenna to have mismatchedimpedances.
 5. An adjustable radio frequency identification device inaccordance with claim 1 and further comprising receiver circuitry havingat least one circuit with at least one selectively tunable circuitelement electrically reconfigurable to modify the reception range of thereceiver circuitry in response to a command from the interrogator unit.6. An adjustable radio frequency identification device in accordancewith claim 5 wherein the at least one circuit comprises a plurality offixed matching networks and circuitry configured to selectively switchone of the fixed matching networks into electrical connection with thereceiver circuitry, in response to the command from the interrogator, inorder to adjust tuning of the receiver circuitry and the antenna.
 7. Anadjustable radio frequency identification device in accordance withclaim 5 wherein the at least one circuit comprises an adjustable circuitelement which selectively causes the receiver circuitry and the antennato have mismatched impedances.
 8. An adjustable radio frequencyidentification device for use with a remote interrogator unit, thedevice comprising: an integrated circuit including receiver circuitryconfigured to receive an interrogation signal from the interrogatorunit; an antenna electrically coupled to the receiver circuitry, theantenna configured to receive the interrogation signal from theinterrogator unit and deliver the interrogation signal to the receiver;and at least one of the antenna and the receiver having reconfigurableelectrical characteristics, the electrical characteristics beingreconfigurable, in response to a command from the interrogator unit, toselectively tune the at least one of the antenna and the receivercircuitry within a range of tuned and detuned states to purposely reducea reception range of the device.
 9. An adjustable radio frequencyidentification device in accordance with claim 8 wherein the receivercircuitry has at least one circuit with at least one selectively tunablecircuit element electrically reconfigurable to modify the receptionrange of the receiver circuitry.
 10. An adjustable radio frequencyidentification device in accordance with claim 9 wherein the at leastone circuit comprises a plurality of fixed matching networks andcircuitry configured to selectively switch one of the fixed matchingnetworks into electrical connection with the receiver circuitry in orderto adjust tuning of the receiver circuitry and the antenna.
 11. Anadjustable radio frequency identification device in accordance withclaim 9 wherein the at least one circuit comprises an adjustable circuitelement which selectively causes the receiver circuitry and the antennato have mismatched impedances.
 12. An adjustable radio frequencyidentification device in accordance with claim 8 and further comprisingtransmitter circuitry having at least one circuit with at least oneselectively tunable circuit element electrically reconfigurable tomodify the transmission range of the transmitter circuitry, in responseto a command from the interrogator unit.
 13. An adjustable radiofrequency identification device in accordance with claim 12 wherein theat least one circuit comprises a plurality of fixed matching networksand circuitry configured to selectively switch one of the fixed matchingnetworks into electrical connection with the transmitter in order toadjust tuning of the transmitter circuitry and the antenna.
 14. Anadjustable radio frequency identification device in accordance withclaim 12 wherein the at least one circuit comprises an adjustablecircuit element which selectively causes the transmitter circuitry andthe antenna to have mismatched impedances.
 15. A method of adapting aradio frequency identification device for use with a remote interrogatorunit, the method comprising: providing transponder circuitry; providingan antenna electrically coupled to the transponder circuitry forcommunicating with a remote interrogator unit; and selectively tuning atleast one of the antenna and the transponder circuitry within a range oftuned and detuned states to purposely reduce sensitivity responsive toan interrogation signal transmitted by the interrogator unit.
 16. Themethod of claim 15 wherein the step of selectively tuning comprisesconfiguring electrical conduction of the transponder circuit.
 17. Themethod of claim 15 wherein the transponder circuit is selectively tunedby electrically switching in one or more of a plurality of fixed circuitnetworks for realizing the desired receiver sensitivity of thecommunication device.
 18. The method of claim 15 wherein the transpondercircuit includes a circuit network, the method further including thestep of selectively tuning the circuit network.
 19. The method of claim15 wherein the transponder circuit comprises a receiver circuit, and thestep of selectively tuning comprises detuning the receiver circuit. 20.The method of claim 15 wherein the transponder circuit comprises atransmitter circuit, with the step of selectively tuning comprisingdetuning the transmitter circuit.
 21. A radio frequency identificationdevice operating method comprising: providing an active transmitterelectrically coupled to an antenna, the transmitter defining at least aportion of a monolithic RFID integrated circuit configured tocommunicate with a remote interrogator; and selectively tuning at leastone of the antenna and the transmitter to a state selected from a rangeof tuned and detuned states to purposely reduce a transmitter range inresponse to a command transmitted by the interrogator unit.
 22. Themethod of claim 21 wherein the transmitter has at least one circuit withat least one selectively tunable circuit element electricallyreconfigurable to modify the transmission range of the transmitter. 23.A radio frequency identification device fabrication method comprising:electrically coupling an active transmitter to an antenna, thetransmitter defining at least a portion of a monolithic RFID integratedcircuit configured to communicate with a remote interrogator; andwherein the transmitter is configured to be selectively tuned to a stateselected from a range of tuned and detuned states to purposely reduce atransmitter range, the selectively tuning including providing aplurality of fixed matching networks and circuitry configured toselectively switch one of the fixed matching networks into electricalconnection with the transmitter, in response to a command transmitted bythe interrogator unit, in order to adjust impedance matching between thetransmitter and the antenna.
 24. The method of claim 22 wherein the atleast one circuit comprises an adjustable circuit element whichselectively causes the transmitter and the antenna to have mismatchedimpedances.
 25. The method of claim 21 wherein the RFID integratedcircuit comprises a receiver having at least one circuit with at leastone selectively tunable circuit element electrically reconfigurable tomodify the reception range of the receiver.
 26. The method of claim 25wherein the at least one circuit comprises a plurality of fixed matchingnetworks and circuitry configured to selectively switch one of the fixedmatching networks into electrical connection with the receiver in orderto adjust tuning of the receiver and the antenna.
 27. The method ofclaim 25 wherein the at least one circuit comprises an adjustablecircuit element which selectively causes the receiver and the antenna tohave mismatched impedances.
 28. An adjustable radio frequencyidentification device for use with a remote interrogator unit, thedevice comprising: a monolithic semiconductor integrated circuit havingintegrated circuitry; transmitter circuitry provided on the monolithicintegrated circuit and forming at least part of the integratedcircuitry; an antenna electrically coupled to the transmitter circuitryand configured to communicate with the remote interrogator unit; and thetransmitter circuitry having reconfigurable electrical characteristics,the electrical characteristics being reconfigurable to selectively tuneat least one of the transmitter circuitry and antenna within a range oftuned and detuned states to purposely reduce a transmission range of theradio frequency identification device.
 29. An adjustable radio frequencyidentification device in accordance with claim 28 wherein thetransmitter circuitry has a plurality of fixed matching networks andcircuitry configured to selectively switch one of the fixed matchingnetworks into electrical connection with the transmitter circuitry inorder to adjust tuning of the transmitter circuitry and the antenna. 30.An adjustable radio frequency identification device in accordance withclaim 28 wherein the transmitter circuitry comprises an adjustablecircuit element which selectively causes the transmitter circuitry andthe antenna to have mismatched impedances.
 31. An adjustable radiofrequency identification device for use with a remote interrogator unit,the device comprising: a semiconductor integrated circuit havingintegrated circuitry; an antenna; transmitter circuitry provided on theintegrated circuit and forming at least part of the integratedcircuitry, the transmitter circuitry having reconfigurable electricalcharacteristics, the electrical characteristics being reconfigurable toselectively tune at least one of the transmitter circuitry and antennawithin a range of tuned and detuned states to purposely reduce atransmission range of the radio frequency identification device; andreceiver circuitry having electrically reconfigurable electricalcharacteristics, the electrical characteristics being reconfigurable toselectively tune at least one of the transmitter circuitry and antennawithin a range of tuned and detuned states to purposely reduce areception range of the radio frequency data communication device.
 32. Anadjustable radio frequency identification device in accordance withclaim 31 wherein the receiver circuitry has a plurality of fixedmatching networks and circuitry configured to selectively switch thefixed matching networks in order to adjust tuning of the receivercircuitry and the antenna.
 33. An adjustable radio frequencyidentification device in accordance with claim 32 wherein thetransmitter circuitry has a plurality of fixed matching networks andcircuitry configured to selectively switch the fixed matching networksin order to adjust tuning of the transmitter circuitry and the antenna.34. An adjustable radio frequency identification device in accordancewith claim 31 wherein the receiver circuitry comprises an adjustablecircuit element which selectively causes the receiver circuitry and theantenna to have mismatched impedances.
 35. An adjustable radio frequencyidentification device in accordance with claim 34 wherein thetransmitter circuitry comprises an adjustable circuit element whichselectively causes the transmitter circuitry and the antenna to havemismatched impedances.
 36. An adjustable radio frequency identificationdevice for use with a remote interrogator unit, the device comprising:an integrated circuit including receiver circuitry configured to receivean interrogation signal from the interrogator unit; an antennaelectrically coupled to the receiver circuitry, the antenna configuredto receive the interrogation signal from the interrogator unit anddeliver the interrogation signal to the receiver circuitry; and thereceiver circuitry having reconfigurable electrical characteristics, theelectrical characteristics being reconfigurable to selectively tune theat least one of the antenna and the receiver circuitry within a range oftuned and detuned states to purposely reduce a reception range of theradio frequency identification device.
 37. An adjustable radio frequencyidentification device in accordance with claim 36 wherein the receivercircuitry has at least one circuit with at least one selectively tunablecircuit element electrically reconfigurable to modify the receptionrange of the receiver circuitry.
 38. An adjustable radio frequencyidentification device in accordance with claim 37 wherein the at leastone circuit comprises a plurality of fixed matching networks andcircuitry configured to selectively switch one of the fixed matchingnetworks into electrical connection with the receiver circuitry in orderto adjust tuning of the receiver circuitry and the antenna.
 39. Anadjustable radio frequency identification device in accordance withclaim 37 wherein the at least one circuit comprises an adjustablecircuit element which selectively causes the receiver circuitry and theantenna to have mismatched impedances.
 40. An adjustable radio frequencyidentification device in accordance with claim 37 and further comprisingtransmitter circuitry having at least one circuit with at least oneselectively tunable circuit element electrically reconfigurable tomodify the transmission range of the transmitter circuitry.
 41. Anadjustable radio frequency identification device in accordance withclaim 40 wherein the at least one circuit comprises a plurality of fixedmatching networks and circuitry configured to selectively switch one ofthe fixed matching networks into electrical connection with thetransmitter circuitry in order to adjust tuning of the transmittercircuitry and the antenna.
 42. An adjustable radio frequencyidentification device in accordance with claim 40 wherein the at leastone circuit comprises an adjustable circuit element which selectivelycauses the transmitter circuitry and the antenna to have mismatchedimpedances.
 43. The adjustable radio frequency identification device ofclaim 1 further comprising a power source electrically coupled to theintegrated circuitry and configured to generate operating power for thecommunications device.
 44. The adjustable radio frequency identificationdevice of claim 8 further comprising a battery electrically coupled tothe integrated circuit and configured to provide power to the receivercircuitry.
 45. The adjustable radio frequency identification device ofclaim 28 further comprising a power source electrically coupled to theintegrated circuitry and configured to generate operating power for thecommunications device.
 46. The adjustable radio frequency identificationdevice of claim 31 further comprising a power source electricallycoupled to the integrated circuitry and configured to generate operatingpower for the radio frequency identification device.
 47. The adjustableradio frequency identification device of claim 36 further comprising abattery electrically coupled to the integrated circuit and configured toprovide power to the receiver circuitry.